The Denver Museum of Nature & Science (Museum) proposes a four-year science education project to investigate the role that degree of citizen science participation has on the learning experience and research outcomes of public participation in science research (PPSR) programs. The long-term objective of the project is to contribute to establishing a best practice for citizen science projects in the content area of human health to better inform the design of future projects in PPSR, both in the Museum's lab, and, importantly, in various settings across the field. This project will take place in the Museum' community-based Genetics of Taste Laboratory (Lab), a unique venue for both citizen science and crowdsourcing health data. These two important aspects of PPSR help to not only serve as entry points for public education about health research, but concurrently serve to advance the creation of new knowledge in the field of public health, making it an ideal venue to conduct this proposed work. The proposed research, education, and evaluation project will assess the quality of citizen science participation, barriers to participation for traditionally underrepresened communities in STEM, and scientific outcomes when gradually building from a collaborative PPSR project to a project that is fully co-created with citizen scientist volunteers. To do so, we will employ both learning research techniques and logic model-based evaluation strategies. With the Lab as the foundation for public engagement, we will conduct four scientific research studies over the course of the science education/learning research project. Each scientific study will be designed to systematically employ a higher degree of citizen scientist participation. At each stage of increased participation will propose asking how citizen scientists are engaging and learning, for whom does this occur, how we can better understand and overcome barriers to participation, and the impact on scientific rigor/quality of data and output. By assessing learning and participation in each stage of engagement in a real and authentic scientific process-from study selection to data collection to data analysis and dissemination-we can move the field closer to its full potential of high-level diverse public participation linked to stronger learning outcomes for participants AND scientific data that is sufficiently precise and accurate for peer-reviewed publications. Successful completion of this project will advance the field of citizen science in two key ways: 1) it will provide pathways for how to strategically integrate all aspects of the scientific research process into PPSR programs while maintaining scientific integrity, and 2) suggest ways to overcome barriers for participation in the various aspects of PPSR, especially among groups historically underrepresented in STEM.